The present invention relates to the manufacture of semiconductor devices. More particularly, the present invention relates to the reduction of post etch gasses or byproducts with the use of an O2/N2 stripping plasma immediately before the wafer is transferred to a wafer carrier, cassette, SMIF pod, Front Opening Unified Pod (FOUP) or other pod.
Semiconductor process tools often stage post-etched wafers with pre-etched wafers in a wafer carrier, cassette, FOUP or other pod. These wafers are not under vacuum, but in the case of containment in a pod are isolated from certain conditions present in the wafer-fab providing enhanced protection against airborne particulates. Typical main chamber processing chemistry involves the use of hydrogen bromide (HBr), chlorine (Cl2) and other gases. Bromides absorbed on the surface of the processed wafers tend to give off gas (outgas) inside the pod at atmospheric conditions and condense as a brominated haze on the unetched wafer surface. These brominated condensates may become an etch defect due to micromasking and may result in yield reduction. A microwave post-etch treatment can eliminate brominated cross contamination caused by the outgas of bromide etched wafers.
The objective of this invention is to reduce the concentration of post-etch gasses and byproducts in the FOUP. To accomplish this objective, the invention applies a post etch plasma to the substrate. The preferred method of application involves the use of a high temperature ashing process using O2/N2 for a short time (approximately 15 seconds). Alternatively a lower temperature and longer process may be used to obtain similar dehalogenation. The ashing process could be done in any manner of asher, but would typically be done in a microwave or RF powered reactor.